In many modern electronic systems, it is necessary to generate multiple output signals at various output frequencies, from one single frequency reference signal. To achieve the desired frequency resolution for modern electronic systems, fractional N-frequency synthesizers are used. In fractional-N frequency synthesizers, a fractional N-frequency divider and associated circuitry are used to establish a division ratio having a fractional component by periodically changing the division ratio of the divider, so that an average value of the output frequency contains a fractional element.
It is known in the art that the use of fractional N-frequency dividers results in undesirable fractional spurs in the output signal of the fractional N-frequency divider. The fractional spurs are a result of the required periodic switching between the different division ratios of the fractional N-frequency divider. Phase compensation circuits, or phase interpolators, are commonly added to a fractional N-frequency divider to smooth the output signal timing in an attempt to mitigate these fractional spurs. However, the phase interpolator must be properly calibrated to provide adequate mitigation of the fractional spurs.
Accordingly, what is needed in the art is a system and method for calibrating the phase interpolator of a fractional N-frequency divider to provide for necessary mitigation of the fractional spurs of the output signal of the fractional N-frequency divider.